A metropolitan area network is a class of network between a local area network and a wide-area network that typically covers an area from the size of a group of small buildings to the size of a large city. For example, a data network using cable television infrastructure may be deployed in one or more neighborhoods, forming a metropolitan area network providing high-speed Internet access.
In recent years, wireless networks based on the IEEE 802.11 standard have been widely deployed to provide high-speed data service across local area networks. Because these systems may be deployed using relatively low-powered radios, it has been possible to embed 802.11 radios in laptops, mobile phones, and other electronic devices. These wireless local area networks have provided convenient, high-speed Internet access in cafes, hotels, businesses, and homes. It is desirable to provide the same convenience available using 802.11 in a local area network across a wider, metropolitan area network.
The IEEE 802.16-2004 standard was promulgated to facilitate development of wireless metropolitan area network systems. While wireless metropolitan area networks may employ technology similar to that used in wireless local area networks, many new technical challenges arise in designing systems that operate effectively over a wider area. The performance of these wireless systems is limited by the link budget between base and remote stations. By increasing the link budget, the overall capacity, coverage, and bandwidth may be improved.
To improve performance of wireless metropolitan area networks, some have proposed employing spatial processing techniques with an antenna array (i.e., an antenna system having multiple antenna elements arranged in any fashion). One such spatial processing technique, beamforming, may be employed to vary the gain and phase characteristics of signals radiated or received by each of the antenna elements to form a radiation pattern designed to attenuate interference and to improve signal gain in one or more directions, thus increasing the link budget and improving system performance.
While beamforming and other spatial processing techniques may be effective, they do not come without cost. These techniques are computation intensive and require hardware support to couple multiple antennas. This additional hardware and computational capability may significantly increase the cost of a wireless system. Accordingly, it is desirable to provide a radio communication system capable of employing spatial processing techniques with reduced hardware support and computational complexity.
As discussed above, it is desirable to increase the capacity and performance of wireless metropolitan area network systems in a cost-effective manner. However, each deployment provides differing requirements. Some wireless metropolitan area networks may need to support large numbers of users in a small geographical area, while other networks may need to support a small number of users over a large geographical area. In addition, the bandwidth requirements of different customers may vary greatly. Instead of designing a system that meets the needs of the most demanding deployments at the expense of less demanding deployments, it is desirable to provide a scalable architecture that can be configured to meet the needs of most wireless network providers.